Greenbank Group has been investing heavily in environment-friendly pipe conveyor technology as a substitute for the still-in-use trough belt conveyors.

01 December 2009

PIPE conveyors provide a suitable solution to address the operational difficulties faced with traditional bulk materials handling systems as well as the need to adopt more stringent environmental controls, says the UK-based Greenbank Group.

“Though trough belt conveyors are still seen as one of the main methods used in the handling of bulk materials, the inherent problems of such conventional systems has prompted many forward-thinking companies such as the Greenbank Group’s materials handling division to invest heavily in the field of pipe conveyor technology, with a view to delivering much more efficient and economical transport solutions,” says Paul Holt, conveyor product manager of Greenbank.

Conventional conveyors have always been plagued with operational issues such as loss of material scattered by wind, velocity disturbance, spillage due to poor alignment, dust creation and spillage at transfer points along the conveyor system, he says. Hence, the focus has been on developing totally enclosed methods of conveying material, concentrating on such operational benefits as carrying it securely and accommodating difficult routing.

Holt believes that the continuing evolution of pipe conveyors is vital in tackling the issues faced by their customers.

>“With increasingly stringent regulations regarding environmental planning, it is imperative we provide solutions that help our customers meet their environmental and social commitments. Our pipe conveyor system is completely enclosed; this means there is minimal contamination to the surrounding environment through spillage or wind scatter of material,” he says. “Additionally, the structural design can generate significant economic savings. The general high level of cleanliness of the system results in much lower maintenance costs and the system can negotiate tight curves and rise at steep inclines, ultimately providing a more economical layout, meaning less need for costly and problematic transfer stations.”

Pipe conveyor systems offer advantages in a number of operational areas in dust control, noise pollution reduction, increased carrying capacity and ability to negotiate tight curves.

Dust control

In the current climate of environmental directives, the pipe conveyor is particularly useful in the control of dust.
“Because the belt is formed around the product, material dust cannot escape and therefore contamination of the surrounding areas and plant is drastically reduced, resulting in much lower maintenance and clean-up costs,” Holt says. “In fact, it is only at the delivery and receiving ends where it may be necessary to provide covers to eliminate dust creation as these are the only areas that are similar in design to those of conventional conveyors. In addition to providing delivery and receiving end covers, dust control filters can also be installed to further reduce dust creation.”

Noise pollution reduction

While drive motors in conveyor systems are typically designed to give a noise level of 85 dbA, the noise level along the route of a pipe conveyor has been measured to be much less than that of a conventional conveyor.

Belt speed

Pipe conveyors generally run faster than their trough counterparts as the material is fully enclosed and also because the tubular belt is inherently stiffer, which results in less belt sag between idlers, thus preventing disturbance of the material being transported.

“It should be noted that belt speed is wholly dependent on idler diameter and rotational speed and since the life of the idler bearing is inversely proportional to its rotational speed, there is an upper limit to belt speed. This is normally set at an idler rotational speed of 1,000 rpm,” Holt explains. “For operational purposes, belt speeds should be kept below this figure and it is recommended that idler rotational speeds are set between 500 and 700 rpm. This gives belt speeds in the order of 150 m/min on smaller diameters and up to 250 m/min on the larger diameter conveyors.”

Coping with curves

In comparison to trough belt conveyors, a pipe system is able to negotiate horizontal and vertical curves of relatively tight radii, thereby eliminating costly and problematic transfer stations.

Whilst the operational and economic benefits of curve handling are obvious, there are still implications of introducing such systems, Holt points out.

“At the standard panel spacing, curves of up to 45 degrees require a radius of 300 times the pipe diameter and up to 600 times for a 90-degree turn. Should tighter radii be required, it is possible to reduce the factor to 200 times the pipe diameter by giving additional support to the belt by reducing the panel spacing. The difficulty is, of course, the deformation of the circular shape at the curve, which, apart from any possible damage to the belt, will reduce the carrying capacity,” he explains.

“As the pipe conveyor travels round a horizontal curve, there is a natural tendency for the belt to twist, displacing the overlap to the inside of the curve when loaded and to the outside of the curve when empty. For this reason, it is necessary to cater for a straight length of conveyor before and after a curve to allow the belt to centre itself.
“This straight length depends on the curve angle and the layout of the conveyor. However, companies like Greenbank, as part of an extensive research and development (R&D) programme, are at the forefront in the research and testing of pipe conveyors systems with significantly reduced radii and at reduced idler spacing to address these restrictions,” he says.

Coping with climbs

He continues: “Along a similar vein as curve handling, pipe conveyors systems are much better suited to coping with steep inclines, enabling handlers to leverage the benefits of maximising the incline angles of their conveyor system.
“Because of the increased contact area between the belt and the material, much steeper angles can be negotiated, allowing a more economical layout. On average, a pipe conveyor will handle materials on an incline which is 50 per cent greater than can be achieved with conventional trough belt conveyors.”


Carrying capacity

In general, a pipe conveyor will carry an equivalent load to a conventional trough belt conveyor which has a width that is three times the pipe’s diameter. However, the maximum capacity of a conventional conveyor also depends on the troughing angle of the idler sets and the surcharge angle of the material being conveyed and, as such, a pipe system may prove even more efficient in particular applications, he adds.

Power

According to Holt, pipe conveyors use approximately 10 per cent of the power absorbed by pneumatic systems and, in theory, 10 to 15 per cent more than a troughed belt conveyor. However in practice, where a straight pipe conveyor is alongside a troughed one, it has been shown that the pipe system has absorbed 15 to 20 per cent less power.
“This saving can be attributed to three key factors: the cleaner environment of the enclosed conveyor which leads to less spillage and hence friction from the idlers, the idlers on the hexagon of the pipe conveyor are not constantly turning, and significantly there is less sag between idlers which reduces the lifting, lowering and disturbance of the material.”

Belt performance
As well as normal cover compounds, various other belt types are available to address such aspects as high temperatures, oil resistance, fire resistance, food quality and abrasion resistance. The majority of conveyor installations use a ply-type belt and the materials used in the manufacture of pipe conveyors are identical to those used on conventional conveyors.

The difference between pipe and conventional trough conveyors is in the construction of the belt itself. “Accurate control of the weft strength is critical to ensure the belt is flexible enough to form the pipe shape whilst still maintaining sufficient strength to prevent collapsing, supporting the load and ensuring resistance to fatigue from flexing. In addition, the plies are closed up at the edges of the belt to reduce edge stiffness, which allows the overlap to form an effective seal.

“As limitations on the tensile strength are similar to those on conventional belts, steel cord belts are available for the larger-capacity pipe systems. These are designed to give the same pipe forming characteristics as the ply belts with breaker plies being used to maintain the pipe shape,” he concludes.

• Pipe conveyors score green point
• Pipes in the groove with sustainability
• DSI acquires wastewater treatment ace
• Masa uses safe pest control techniques
• Autodesk portfolio boosts efficiency

Tags

Regional News UAE Focus Expo News Legally Bound Architectural Focus Kuwait Review Makkah & Madinah Environment Protection Scaffolding & Formwork Insulation Bathrooms Transport & Materials Handling Project Watch Diary Of Events Tenders

Gulf Construction is the undisputed leading trade journal for the building and construction industries of Saudi Arabia and the other Gulf states. The magazine provides editorial coverage on a wide range of topics which are of interest to industry professionals. In addition, regular features highlight technological developments within specific industry fields. Launched 40 years ago, the magazine has established an enviable reputation as an authoritative, respected journal with unmatched coverage of the Gulf region. Gulf Construction is essential reading for anyone with a serious interest in the region’s building and construction industry.